Preliminary evaluation of certain benzylidine and pyrazole derivatives against wood decay fungi

Three benzylidine derivatives; dibenzylidineacetone (1,5-diphenyl penta-1,4dien-3–one) (1); dibenzylidine acetylacetone (1,7-diphenyl hepta-1,6-dien-3,5– dione) (2) and benzylidine acetophenone (1,3-diphenyl propen-3–one) (Chalcone) (3) as well as three pyrazole derivatives; 3,5-dimethylpyrazole (4), 3-methyl-1-phenylpyrazol-5-one (5) and 3-methyl-1-(2,4-dinitrophenyl)pyrazol-5-one (6) were evaluated for their fungitoxic effects against the white rot fungus Coriolus versicolor and the brown rot fungus Gloeophyllum trabeum. In vitro measurements, relationship between the chemical structure and the fungitoxicity of both studied derivatives was conducted. Compound 6 was the most active derivative with IC₅₀ of 19.6 µg/ml against C. versicolor and 112.7 µg/ml against G. trabeum. The two active compounds (compounds 3 and 6) were tested in vivo on poplar wood (Populus nigra) and Scots pine sapwood (Pinus sylvestris) specimens using mini-blocks technique. Different concentrations of these compounds were examined using C. versicolor and G. trabeum for leached and unleached wood samples. After six weeks of fungal exposure, compound 6 proved a significant effectiveness against both tested fungi with mass loss ± SE equaled 13.67% ± 0.54 and 14.47% ± 0.34 in case of C. versicolor and G. trabeum, respectively in the unleached specimens comparing with 41.27% ± 0.43 and 41.53% ± 0.42 in control. These mass loss percentages were 23.87% ± 0.61 and 24.80% ± 0.35 in case of compound 3 in the same array. Their performance in leached samples was detected for both tested compounds with percentage of mass loss exceeded 25% for the two wood specimens under investigation.